PTPA and small cell lung carcinoma: MUC1‐C was found to upregulate the expression of ASCL1 and NEUROD1 through MYC activation.[38] Meanwhile, MUC1 is involved in promoting inflammation.[85] MUC1 activates PP2A and inhibits downstream protein phosphorylation in three different subtypes of SCLC cell lines, suggesting that the MUC1–PP2A axis is a conserved regulatory mechanism across all SCLC subtypes.